JPH044366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method of operating a hot blast furnace that blows air into a blast furnace.

"Prior Art" A hot blast furnace, which is one of the auxiliary equipment of a blast furnace in a steelworks, is a large-capacity heat exchanger for generating hot air that is used as a heat source for the blast furnace and for burning coke in the blast furnace.

Usually, 4 to 5 hot blast furnaces are installed in each blast furnace, and some of these always burn fuel gas in the combustion chamber inside the furnace to heat the refractory material in the heat storage chamber inside the furnace, and the other hot blast furnaces Hot air of 900-1300℃ is sent to the blast furnace.

FIG. 5 is a block diagram showing a conventional method of operating a hot air stove when there are four hot air stoves.

As shown in the drawing, two hot air stoves 1A and 1B are in a firing state (diagonal lines in the drawing indicate that they are in a burning state), and the other two hot air stoves 1C,
When 1D is in the blowing state, the hot air sent from the hot air stoves 1C, 1D by the operation of the blower 2 is sent to the hot air stoves 1C, 1D in the blowing state so that the reading of the thermometer 3 becomes the set blowing temperature. Each cold air butterfly valve 4
The opening degrees of C and 4D are calculated by the calculator 5 to control the opening and closing, and when switching the blowing furnace to a new furnace, when the temperature of the hot air sent to the blast furnace tends to increase, The cold air separately sent from the blower 2 is mixed through a mixing valve (not shown) and adjusted so that the reading of the thermometer 3 is always maintained at the set temperature and the hot air is sent at the desired temperature. For example, as a blowing temperature control method for hot air stoves,
It is disclosed in Publication No. 117302.

Note that 4A and 4B in FIG. 5 are the cold air butterfly valves of the hot air stoves 1A and 1B which are in the combustion state and are closed.

"Problems to be solved by the invention" In recent years, high fuel ratio operations have been carried out in which a large amount of coke is charged into the blast furnace in order to obtain a large amount of blast furnace gas. However, in order to lower the blowing temperature, it is common to reduce the amount of fuel input into the combustion chamber of the hot-blast stove when the hot-blast stove is in a combustion state.

However, when the input fuel is reduced, the lower temperature of the silica brick part 7 of the heat storage chamber 6 of the hot air stove 1, schematically shown in FIG.
Since the temperature drops to below 400°C and there is a risk of brick damage, it is not possible to reduce the amount of input fuel, and there is a limit to reducing the blast temperature by controlling the fuel.

Therefore, it may be possible to increase the mixed amount of cold air from the mixed cooling valve (not shown), but the mixed cooling valve is usually a small-capacity valve installed for adjustment when supplying high-temperature hot air to the blast furnace. Since it is common that
It is not possible to send a large amount of cold air, and there is a limit to how much the air temperature can be lowered by such means.

Therefore, it is conceivable to increase the capacity of the mixed cooling valve, but the piping system must also have a large diameter, which poses the problem of increased equipment costs.

As described above, the current situation is that a technology has not yet been developed that can inexpensively and easily operate to obtain a blowing temperature of about 700°C, which is lower than the conventional operation that obtains a blowing temperature of about 1100°C.

The present invention aims to solve the conventional problems as described above, and as a result of intensive research, the number of operating hot blast furnaces that maximizes the temperature and efficiency of blowing air to the blast furnace (furnaces in combustion state) is determined based on past operational data. As shown in Figure 4, we found that there is a close relation between By sending hot air and sending cold air through the redundant hot air stove, it is possible to easily achieve a low air temperature.
It was also found that operation can be easily performed at any air blowing temperature due to changes in operation.

``Means for Solving the Problems'' The present invention is aimed at, in the operation of a hot blast furnace that blows air from a plurality of furnaces, to combine the hot air sent from a predetermined number of furnaces according to the set value of the temperature for blowing air into the blast furnace and the surplus. It is characterized by adjusting the mixing ratio with the cold air sent from the furnace and sending the air to the blast furnace.

``Effect'' When the temperature of the air blown to the blast furnace is particularly low, by sending cold air through the surplus hot blast furnace, the hot blast furnace can be operated without installing special equipment, and the hot blast furnace can be overheated. It is possible to avoid damaging the silica bricks in the heat storage chamber by blowing cold air.

"Example" Below, an example of the present invention will be described based on the drawings.

FIG. 1 is a block diagram in the case where there are four hot air stoves to which the present invention is applied, and two of them are in the air blowing state.

In the drawings, each hot air stove 1A, 1B, 1C, 1
D, blower 2, thermometer 3, each butterfly valve 4A,
4B, 4C, 4D and the arithmetic unit 5 are exactly the same as those in the conventional example shown in FIG.

Further, 8 is a thermometer installed in the lower layer of the silica brick part 7 of the heat storage chamber 6, and when the reading of one of the thermometers 8 installed in the furnace in the air blowing state becomes 400°C or less, a cold air butterfly valve is activated. The opening degree of the cold air butterfly valve 4A is calculated by the calculator 9, and when the readings of the thermometer 8 both exceed 400°C and further exceed a predetermined temperature, the opening degree of the cold air butterfly valve 4A is calculated by the calculator 9. It is designed to be calculated and closed by .

Next, an example of the method of operating the hot air stove of the present invention will be described in the case where the blowing temperature is changed from 1100°C to 700°C.

As shown in Fig. 4, when the air blowing temperature is 700°C, the number of hot air stoves operating at maximum efficiency is three, so in Fig.
C and 1D, and the hot air stove in the combustion state is 1B.
Then, the hot air stove 1A is changed from the combustion state to the surplus furnace (the diagonal lines in the drawing indicate the furnace in the combustion state, and the mesh indicates the surplus furnace).

As in the conventional example, the cold air butterfly valve 4C,
Opening/closing control is performed by calculating the opening degree of 4D by the calculator 5. At this time, if the reading of one of the thermometers 8 of the furnaces 1C and 1D which are in the blowing state falls below 400°C, the cold air butterfly valve 4A is activated. opens, cold air is sent into the surplus furnace 1A, lowering the reading on the thermometer 3, and as a result, the butterfly valves 4C and 4D are adjusted to lower the amount of cold air supplied to the furnaces 1C and 1D, which are in the blowing state, and both temperatures are lowered. A total of 8 readings are always maintained above 400°C.

Note that if the reading of one or both of the thermometers 8 does not exceed 400°C even after a predetermined period of time has elapsed,
The opening degree of the cold air butterfly valve 4A is further adjusted further until the reading of each thermometer 8 exceeds 400°C.

And the readings of the thermometer 8 are both 400°C.
This state is maintained until the temperature exceeds a predetermined temperature.

In addition, although this example describes the case of a low air blowing temperature of 700°C, it is also possible to use high-temperature air blowing when changing to a blast furnace or increasing production operation, adjusting the hot metal temperature or hot metal composition, or sucking powder from the tuyere. Of course, if you want to obtain the desired temperature, you can adjust the number of hot air stoves in operation depending on the number of hot stoves you have, or you can select and adopt the conventional temperature adjustment using a mixed cooling valve as appropriate.

In this way, hot air at 700°C is sent to the blast furnace.

In addition, Fig. 2 shows changes over time in the blowing temperature A before and after changing the blowing temperature in this example, and the temperature B of the lower layer of the silica brick part in the preceding furnace in the hot blast furnace in the blowing state. This shows that the lower temperature of the brick part was maintained on the control line, and the air was blown at a temperature of 700°C after the air blowing temperature was changed.

As described above, according to the operating method of the present invention,
It is inexpensive and can easily obtain a low blowing temperature.

In addition, it has become possible to freely obtain high or low air blowing temperatures according to the operational preference of the blast furnace without modifying the equipment.

[Brief explanation of drawings]

Fig. 1 is a block diagram when there are four hot air stoves to which the present invention is applied, and Fig. 2 shows the air blowing temperature before and after changing the air blowing temperature in this embodiment, and the inside of the hot air stove in the blowing state. Fig. 3 is a schematic diagram of the heat storage chamber of the hot-blast stove, and Fig. 4 shows the relationship between the blowing temperature and the number of operating units of the hot-blast stove that maximizes efficiency. A diagram showing the relationship,
FIG. 5 is a block diagram showing a conventional example of hot blast stove operation. 1A, 1B, 1C, 1D...Hot stove, 2...Blower, 3...Thermometer, 4A, 4B, 4C, 4D...
... Butterfly valve, 5, 9 ... Arithmetic unit, 6 ... Heat storage chamber, 7 ... Silica brick section, 8 ... Thermometer.

Claims (1)

[Claims] 1. In the operation of a hot blast furnace that blows air from multiple furnaces, the mixing ratio of the hot air sent from a predetermined number of furnaces and the cold air sent from surplus furnaces is adjusted according to the set value of the temperature blowing to the blast furnace. A method of operating a hot blast furnace characterized by blowing air into a blast furnace.